Butted sensor array with supplemental chip in abutment region

ABSTRACT

The present invention relates to photosensitive chips for creating electrical signals from an original image, as would be found for example in a digital scanner, copier, facsimile machine, or other document generating or reproducing device. More specifically, the present invention relates to preferably providing a supplemental chip in each abutment region to enhance image quality.

FIELD OF THE INVENTION

The present invention relates to photosensitive chips for creatingelectrical signals from an original image, as would be found for examplein a digital scanner, copier, facsimile machine, or other documentgenerating or reproducing device. More specifically, the presentinvention relates to preferably providing a supplemental photosensitivechips in abutment regions to enhance image quality.

BACKGROUND OF THE INVENTION

Image sensor arrays typically comprise a linear array of photosensorswhich raster scan an image bearing document and convert the microscopicimage areas viewed by each photosensor to image signal charges. Eachphotosensor collects light from a corresponding photosite. Following anintegration period, the image signal charges are amplified andtransferred as an analog video signal to a common output line or busthrough successively actuated multiplexing transistors. One example ofsuch an array is a charged-coupled device (CCD).

For high-performance image sensor arrays, a preferred design includes anarray of photosites of a width comparable to the width of a page beingscanned, to permit one-to-one imaging generally without the use ofreductive optics. In order to provide such a “full-width” array,however, relatively large silicon structures must be used to define thelarge number of photosites. A preferred technique to create such a largearray is to align several butted silicon chips, each chip defining asmall linear array thereon.

The silicon chips which are butted to form a single full-width array aretypically created by first creating the circuitry for a plurality ofindividual chips on a single silicon wafer. The silicon wafer is thencut or “diced,” around the circuit areas to yield discrete chips.Typically, the technique for dicing the chips includes a combination ofchemical etching and mechanical sawing. On each chip, photosites arespaced from one end of a chip to the other; the length of each dicedchip from one end of the array thereon to the other requires precisiondicing. It would be desirable to dice each individual chip with aprecise dimension along a linear array of photosites, so that, when aseries of chips are butted end-to-end to form a single page-width lineararray, there is a minimum disruption of spacing from an end photosite onone chip to a neighboring photosite at the end of a neighboring chip.This minimum disruption of spacing is referred to as an abutment region.Ideally, the pitch, across an entire full-width linear array should beconsistent regardless of the configuration of silicon chips forming thearray. Pitch is the distance between the center points of two adjacentphotosites.

Preferably, the full-width array extends the entire length of adocument, such as eleven inches. Usually, the full-width array is usedto scan line by line across the width of a document with the documentbeing moved or stepped lengthwise in synchronism therewith. A typicalarchitecture for such a sensor array is given, for example, in U.S. Pat.No. 5,473,513. When the original document moves past the full-widtharray, each of the photosites receives reflected light and thecorresponding photosensors convert reflected light from the originalimage into electrical signals. The motion of the original imageperpendicular to the linear array causes a sequence of signals to beoutput from each photosensor, which can be converted into digital data.

With the gradual introduction of color-capable products into the officeequipment market, it has become desirable to provide scanning systemswhich are capable of converting light from full-color images intoseparate trains of image signals, each train representing one primarycolor. In order to obtain the separate signals relating to colorseparations in a full-color image, one technique is to provide on eachsemiconductor chip multiple parallel linear arrays of photosites withcorresponding photosensors, each of the parallel arrays being sensitiveto one primary color. Typically, this arrangement can be achieved byproviding multiple linear arrays of photosites which are physicallyidentical except for a translucent primary-color overlay over photositesfor that linear array. In other words, the linear array which issupposed to be sensitive to red light only will have a translucent redlayer placed on the photosites thereof, and such would be the case for ablue-sensitive array and a green-sensitive array. Although it ispreferable to use three linear arrays, any number of linear arrays canbe used. As the chips are exposed to an original full-color image, onlythose portions of the image, which correspond to particular primarycolors, will reach the photosensors assigned to the primary color. Thus,the photosite determines what portions of the image will reach thephotosensors.

The most common substances for providing these translucent filter layersover the photosites is polyimide or acrylic. For example, polyimide istypically applied in liquid form to a batch of photosensitive chipswhile the chips are still in undiced, wafer form. After the polyimideliquid is applied to the wafer, the wafer is centrifuged to provide aneven layer of a particular polyimide. In order to obtain the polyimidehaving the desired primary-color-filtering properties, it is well knownto dope the polyimide with either a pigment or dye of the desired color,and these dopants are readily commercially available. When it is desiredto place different kinds of color filters on a single chip, a typicaltechnique is to first apply an even layer of polyimide over the entiremain surface of the chip (while the chip is still part of the wafer) andthen remove the unnecessary parts of the filter by photo-etching oranother well known technique. Typically, the entire filter layer placedover the chip is removed except for those areas over the desired set ofphotosites. Acrylic is applied to the wafer in a similar manner.

In the prior art, there was a problem in that the edge photosites of thechips may not capture all of the reflected light in the abutment region.Therefore, the corresponding photosensors would not convert all of thereflected light from the original image into electrical signals.Although U.S. patent application Ser. Nos. 09/039,523, 09/282,317,09/211,761 and 09/211,765, have provided alternative techniques toimprove image quality, there is a continuing need to enhance imagequality by capturing as much of the reflected light from the originalimage as possible, so that the corresponding photosensors can accuratelyconvert the original image into electrical signals for conversion todigital data to enhance image quality.

SUMMARY OF THE INVENTION

An assembly including a substrate; a plurality of butted photosensitivechips mounted to the substrate, wherein each photosensitive chip has anedge photosite and wherein an abutment region is formed between the edgephotosites of butted photosensitive chips; and at least onephotosensitive chip mounted to the substrate and butted to twophotosensitive chips along the abutment region. Each photosensitive chiphas a plurality of edge photosites. Each of the photosensitive chipsdefines a plurality of photosites evenly spaced thereon, the photositesbeing positioned to form a linear array on the substrate. Each of thesupplemental photosensitive chips defines a plurality of photositesevenly spaced thereon.

Alternatively, each of the photosensitive chips defines a plurality ofphotosites evenly spaced thereon, the photosites being positioned toform multiple parallel linear arrays on the substrate. Each linear arrayis covered by a different translucent filter. Each of the supplementalphotosensitive chips defines a plurality of photosites evenly spacedthereon, the photosites being positioned and covered with translucentfilter materials to correspond with multiple parallel linear arraysformed by the photosensitive chips.

A document generating device including a raster input scanner scanningdocuments to generate digital image signals, the raster input scannerincluding a photosensitive chip assembly having photosensitive chips andsupplemental photosensitive chips mounted to a substrate; aphotoreceptor; a controller; a raster output scanner, being directed bythe controller to expose the photoreceptor to create an electrostaticlatent image based on the digital image signals received from the rasterinput scanner; a developer developing the latent image; a transfer unittransferring the developed image to a support material; and a fuser unitpermanently affixing the developed image on the support material. Thephotoreceptor can be a photoconductive belt. The document generatingdevice may further include a plurality of raster output scannersdirected by the controller to expose the photoreceptor to create thelatent image; and a plurality of developers, each developer applying adifferent color to develop the latent image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a base substrate having a plurality ofbutted chips mounted thereon to form a photosensitive chip assembly;

FIG. 2 is a plan view showing an example of a photosensitive chip usedin the present invention;

FIG. 3 is a perspective view showing an example of two photosensitivechips used in the present invention;

FIG. 4 is a perspective view of a semiconductor wafer relevant to thepresent invention;

FIG. 5 is a blow up of two butted photosensitive chips and asupplemental photosensitive chip butted to the two photosensitive chipsforming a photosensitive chip assembly in accordance with the presentinvention;

FIG. 6 is a partial schematic elevational view of a first example of adigital copier, which can employ the photosensitive chip assembly of thepresent invention; and

FIG. 7 is a partial schematic elevational view of a second example of adigital copier, which can employ the photosensitive chip assembly of thepresent invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

FIG. 1 shows a plurality of photosensitive chips 10 mounted and buttedon a substrate 20 from end to end to form an effective collinear arrayof photosites, which extends across a page image being scanned for ascanner, copier, facsimile machine or other document reading orgenerating device. Thus, the plurality of chips 10 mounted to substrate20 forms a full-width array. Generally, each individual photositereceives reflected light and each corresponding photosensor is adaptedto output a charge or voltage signal indicative of the intensity oflight of a certain type received through the photosite; variousstructures, such as transfer circuits, or charged coupled devices, areknown in the art for processing signal output by the various photosites.A plurality of supplemental photosensitive chips 11 are also mounted ona substrate 20 to augment the full-width array. Preferably, eachsupplemental photosensitive chip 11 is butted against two photosensitivechips 10 in the abutment region as shown in FIG. 1. The photosensitivechips 10 and supplemental photosensitive chips 11 mounted to substrate20 form a photosensitive chip assembly. Preferably, the number ofsupplemental photosensitive chips 11(M) is one less than the number ofphotosensitive chips 10(N), where M and N are whole numbers.

FIG. 2 is a plan view showing one of these photosensitive chips 10relevant to the claimed invention. The chip 10 is generally made of asemiconductor substrate, as is known in the art, in which circuitry andother elements are formed, such as by photolithographic etching. A fewof the most relevant structures are one or more linear arrays ofphotosites 12, each of which forms the photosensitive surface ofcircuitry within the chip 10, and a set of bonding pads 14. Thephotosites 12 are typically arranged in a linear array along one maindimension of the chip 10, with each photosite 12 along the arraycorresponding to one pixel in an image signal. As will be described indetail below, the photosites 12 are preferably for sensing the threeprimar lors, blue, green and red. Photosites, which sense blue, greenand red, are referred to as photosites 12B, 12G and 12R. Each photositeis associated with a corresponding photosensor. Preferably, thephotosites are uniformly spaced to provide a uniform pitch, whichenhances digital signal processing. Pitch is the distance between thecenter of one photosite and the center of an adjacent photosite.Preferably, there are three parallel linear arrays 16 a, 16 b, and 16 cfor the three primary colors. However, any number of linear arrays maybe utilized. For example, only one linear array could be placed on thechip 10 for use in a monochrome scanner, copier, printer, etc.

The bonding pads 14 are distinct surfaces on the main surface of thechip 10, and are intended to accept wire bonds attached thereto. Thebonding pads 14 thus serve as the electronic interface between the chip10 and any external circuitry. The circuitry for obtaining signalsrelated to light directed to the photosites 12, and for unloading imagedata from the chip 10 is generally indicated as 15. The circuitry 15 isgenerally deposited between the linear array of photosites 12 and alinear array of bonding pads 14.

Chips 10 are typically formed in batches on semiconductor wafers, whichare subsequently cleaved, or “diced,” to create individual chips.Typically, the semiconductor wafers are made of silicon. As is known inthe art, photolithographically etched V-grooves 18 define precisely theintended boundaries of a particular chip 10 for dicing as shown in theperspective view of two adjacent chips 10 in FIG. 3. Thus, all of thephotosites 12, bonding pads 14 and circuitry 15 for relatively largenumber of chips 10 are etched simultaneously onto a single semiconductorwafer. The region between the V-grooves 18 is called the tab region. Thephotosites 12 adjacent to each V-groove in FIG. 3 (adjacent to the edgeas shown in FIG. 2) are referred to as an edge or outer photosites. Theother photosites 12 are referred to as inner photosites.

FIG. 4 shows a typical semiconductor wafer 30, in isolation, wherein arelatively large number of chips 10 are created in the wafer 30 prior todicing thereof. Each chip 10 has a distinct chip area within the mainsurface of the wafer 30. The phrase “chip area” refers to a defined areawithin the main surface of the wafer 30 which is intended to comprise adiscrete chip 10 after the dicing step, when individual chips 10 (FIG.2) are separated from the rest of the wafer 30.

Although the structure and manufacturing techniques of thephotosensitive chip 10 have been discussed with reference to FIGS. 2through 4, the same or similar techniques and structures may be used toprovide the supplemental photosensitive chips 11.

FIG. 5 shows a blow up of two butted photosensitive chips 10 and asupplemental photosensitive chip 11 butted to the two photosensitivechips 10 along the abutment region in FIG. 1. As discussed above, all ofthese chips are mounted to a substrate 20 forming a photosensitive chipassembly in accordance with the present invention. As shown in FIG. 5, afew of the most relevant structures are one or more linear arrays ofphotosites 12, each of which forms the photosensitive surface ofcircuitry within the supplemental photosensitive chip 10, and a set ofbonding pads 14. The photosites 12 are typically arranged in a lineararray along one main dimension of the chip 10, with each photosite 12along the array corresponding to one pixel in an image signal. Thephotosites 12 are preferably for sensing the three primary colors, blue,green and red. Photosites 12, which sense blue, green and red, arereferred to as photosites 12B, 12G and 12R. Each photosite is associatedwith a corresponding photosensor. Preferably, the photosites areuniformly spaced to provide a uniform pitch, which enhances digitalsignal processing. Pitch is the distance between the center of onephotosite and the center of an adjacent photosite. Preferably, there arethree parallel linear arrays 16 a, 16 b, and 16 c for the three primarycolors. However, any number of linear arrays may be utilized. Forexample, only one linear array could be placed on the supplementalphotosensitive chip 11 for use in a monochrome scanner, copier, printer,etc.

The bonding pads 14 are distinct surfaces on the main surface of thesupplemental photosensitive chip 11, and are intended to accept wirebonds attached thereto. The bonding pads 14 thus serve as the electronicinterface between the supplemental photosensitive chip 11 and anyexternal circuitry. The circuitry for obtaining signals related to lightdirected to the photosites 12, and for unloading image data from thesupplemental photosensitive chip 11 is generally indicated as 15. Thecircuitry 15 is generally deposited between the linear array ofphotosites 12 and a linear array of bonding pads 14.

When the photosensitive chips 10 and supplemental photosensitive chips11 are mounted to the substrate 20 to form the photosensitive chipassembly, the one or more linear arrays 16 of the supplementalphotosensitive chips 11 are preferably two to twelve scan lines awayfrom the one or more linear arrays 16 in the photosensitive chips 10.Preferably, the photosensitive chips 10 and supplemental photosensitivechips 11 are parallel to each other and in the same plane. Preferably,the number of photosites 12 in each linear array on the supplementalphotosensitive chip 11 is three. However, there may be additionalphotosites 12 depending on the distance between the edge photosites 12of the two photosensitive chips 10 (the length of the abutment region).This chip assembly has the advantage of potentially increasing the gapbetween the edges of photosensitive chips 10. This decreases thetolerance sensitivity of photosensitive chip placement.

When a document is scanned, the reflected light from an original imageis received by the photosites of the photosensitive chip assembly, thecorresponding photosensors provide electrical signals, which areconverted into digital data. Before combining digital data generated bythe supplemental photosensitive chips 11 with digital data generated bythe photosensitive chips 10, digital data generated by the supplementalphotosensitive chips 11 is preferably interpolated to minimize any dataerrors due to misalignment errors between the photosites 12 on thephotosensitive chip 10 and the photosites 12 on the supplementalphotosensitive chip 11. These misalignment errors are positional errorscaused by misplacement of the chips 10 and 11.

FIG. 6 is a partial schematic view of an example of a digital imagingsystem, such as the digital imaging system of U.S. application Ser. No.08/838,630, including a scanner, which can utilize the assembly ofphotosensitive chips 10 and supplemental photosensitive chips 11. Itwill be understood, however, that it is not intended to limit theinvention to the embodiment disclosed. On the contrary, it is intendedto cover all alternatives, modifications and equivalents as may beincluded within the spirit and scope of the invention as defined by theappended claims.

An original document is positioned in a document handler 227 on araster-input scanner (RIS) indicated generally by reference numeral 228.The RIS 228 contains document illumination lamps, optics, a mechanicalscanning device and a photosensitive chip assembly of the presentinvention. The photosensitive chips 10 and supplemental photosensitivechips 11 may include a linear array of photosites or multiple parallellinear arrays of photosites as described above. The RIS 228 captures theentire original document and converts it to a series of raster scanlines. This information is transmitted to an electronic subsystem (ESS)or controller 229 which controls a raster output scanner (ROS) 230.

The digital imaging system employs a photoconductive belt 210.Preferably, the photoconductive belt 210 is made from a photoconductivematerial coated on a ground layer, which, in turn, is coated on ananti-curl backing layer. Belt 210 moves in the direction of arrow 213 toadvance successive portions sequentially through the various processingstations deposited about the path of movement thereof. Belt 210 isentrained about stripping roller 214, tensioning roller 220 and driveroller 216. As roller 216 rotates, it advances belt 210 in the directionof arrow 213.

Initially, a portion of the photoconductive surface passes throughcharging station A. At charging station A, a corona generating deviceindicated generally by the reference numeral 222 charges thephotoconductive belt 210 to a relatively high, substantially uniformpotential.

At an exposure station B, a controller or electronic subsystem (ESS) 229receives the image signals representing the desired output image andprocesses these signals to convert them to a continuous tone orgrayscale rendition of the image which is transmitted to a modulatedoutput generator, for example the raster output scanner (ROS), indicatedgenerally by reference numeral 230. Preferably, ESS 229 is aself-contained, dedicated minicomputer. The image signals transmitted toESS 229 may originate from a RIS 228 as described above or another typeof scanner utilizing the photosensitive chips 10, thereby enabling theabsorption to serve as a remotely located printer for one or morescanners. Alternatively, the printer may serve as a dedicated printerfor a high-speed computer or for one or more personal computers. Thesignals from ESS 229, corresponding to the continuous tone image desiredto be reproduced by the printer, are transmitted to ROS 230. ROS 230includes a laser with rotating polygon mirror blocks. The ROS 230 willexpose the photoconductive belt 210 to record an electrostatic latentimage thereon corresponding to the continuous tone image received fromESS 229. As an alternative, ROS 230 may employ a photosensitive array oflight emitting diodes (LEDs) arranged to illuminate the charged portionof photoconductive belt 210 on a raster-by-raster basis.

After the electrostatic latent image has been recorded onphotoconductive surface 212, belt 210 advances the latent image to adevelopment station, C, where toner, in the form of liquid or dryparticles, is electrostatically attracted to the latent image usingcommonly known techniques. The latent image attracts toner particlesfrom the carrier granules forming a toner powder image thereon. Assuccessive electrostatic latent images are developed, toner particlesare depleted from the developer material. A toner particle dispenser,indicated generally by the reference numeral 244, dispenses tonerparticles into developer housing 246 of developer unit 238.

With continued reference to FIG. 6, after the electrostatic latent imageis developed, the toner powder image present on belt 210 advances totransfer station D. A print sheet 248 is advanced to the transferstation, D, by a sheet feeding apparatus, 250. Preferably, sheet feedingapparatus 250 includes a nudger roll 251 which feeds the uppermost sheetof stack 254 to nip 255 formed by feed roll 252 and retard roll 253.Feed roll 252 rotates to advance the sheet from stack 254 into verticaltransport 256. Vertical transport 256 directs the advancing sheet 248 ofsupport material into the registration transport 290 and past imagetransfer station D to receive an image from photoreceptor belt 210 in atimed sequence so that the toner powder image formed thereon contactsthe advancing sheet 248 at transfer station D. Transfer station Dincludes a corona-generating device 258, which sprays ions onto thebackside of sheet 248. This attracts the toner powder image fromphotoconductive surface 212 to sheet 248. The sheet is then detachedfrom the photoreceptor by corona generating device 259 which spraysoppositely charged ions onto the back side of sheet 248 to assist inremoving the sheet from the photoreceptor. After transfer, sheet 248continues to move in the direction of arrow 260 by way of belt transport262, which advances sheet 248 to fusing station F.

Fusing station F includes a fuser assembly indicated generally by thereference numeral 270 which permanently affixes the transferred tonerpowder image to the copy sheet. Preferably, fuser assembly 270 includesa heated fuser roller 272 and a pressure roller 274 with the powderimage on the copy sheet contacting fuser roller 272. The pressure roller274 is loaded against the fuser roller 272 to provide the necessarypressure to fix the toner powder image to the copy sheet. The fuserroller 272 is internally heated by a quartz lamp (not shown). Releaseagent, stored in a reservoir (not shown), is pumped to a metering roll(not shown). A trim blade (not shown) trims off the excess releaseagent. The release agent transfers to a donor roll (not shown) and thento the fuser roll 272. Or alternatively, release agent is stored in apresoaked web (not shown) and applied to the fuser roll 272 by pressingthe web against fuser roll 272 and advancing the web at a slow speed.

The sheet then passes through fuser 270 where the image is permanentlyfixed or fused to the sheet. After passing through fuser 270, a gate 280either allows the sheet to move directly via output 284 to a finisher orstacker, or deflects the sheet into the duplex path 300, specifically,first into single sheet inverter 282 here. That is, if the sheet iseither a simplex sheet, or a completed duplex sheet having both side oneand side two images formed thereon, the sheet will be conveyed via gate280 directly to output 284. However, if the sheet is being duplexed andis then only printed with a side one image, the gate 280 will bepositioned to deflect that sheet into the inverter 282 and into theduplex loop path 300, where that sheet will be inverted and then fed toacceleration nip 202 and belt transports 310, for recirculation backthrough transfer station D and fuser 270 for receiving and permanentlyfixing the side two image to the backside of that duplex sheet, beforeit exits via exit path 284.

After the print sheet is separated from photoconductive surface 212 ofbelt 210, the residual toner/developer and paper fiber particlesadhering to photoconductive surface 212 are removed therefrom atcleaning station E. Cleaning station E includes a rotatably mountedfibrous brush in contact with photoconductive surface 212 to disturb andremove paper fibers and a cleaning blade to remove the nontransferredtoner particles. The blade may be configured in either a wiper or doctorposition depending on the application. Subsequent to cleaning, adischarge lamp (not shown) floods photoconductive surface 212 with lightto dissipate any residual electrostatic charge remaining thereon priorto the charging thereof for the next successive imaging cycle.

Controller or ESS 229 regulates the various printer functions. Thecontroller or ESS 229 is preferably a programmable microprocessor, whichcontrols all of the printer functions hereinbefore described. Thecontroller or ESS 229 provides a comparison count of the copy sheets,the number of documents being recirculated, the number of copy sheetsselected by the operator, time delays, jam corrections, etc. The controlof all of the exemplary systems heretofore described may be accomplishedby conventional control switch inputs from the printing machine consolesselected by the operator. Conventional sheet path sensors or switchesmay be utilized to keep track of the position of the document and thecopy sheets.

FIG. 7 is a partial schematic view of another example of a digitalimaging system, such as the digital imaging system of U.S. applicationSer. No. 09/220,972, including a scanner, which can utilize the assemblyof photosensitive chip 10 and supplemental photosensitive chips 11. Theimaging system is used to produce color output in a single pass of aphotoreceptor belt. It will be understood, however, that it is notintended to limit the invention to the embodiment disclosed. On thecontrary, it is intended to cover all alternatives, modifications andequivalents as may be included within the spirit and scope of theinvention as defined by the appended claims, including a multiple passcolor process system, a single or multiple pass highlight color systemand a black and white printing system.

In this embodiment, an original document can be positioned in a documenthandler 427 on a raster-input scanner (RIS) indicated generally byreference numeral 428. The RIS 428 contains document illumination lamps,optics, a mechanical scanning device and a photosensitive chip assemblyof the present invention. The photosensitive chips 10 and supplementalphotosensitive chips 11 may include a linear array of photosites 12 ormultiple parallel linear arrays of photosites 12 as described above. TheRIS 428 captures the entire original document and converts it to aseries of raster scan lines. This information is transmitted to anelectronic subsystem (ESS) or controller 490 which controls a rasteroutput scanner (ROS) 424.

The printing machine uses a charge retentive surface in the form of anActive Matrix (AMAT) photoreceptor belt 410 supported for movement inthe direction indicated by arrow 412, for advancing sequentially throughthe various xerographic process stations. The belt is entrained about adrive roller 414, tension rollers 416 and fixed roller 418 and the driveroller 414 is operatively connected to a drive motor 420 for effectingmovement of the belt through the xerographic stations. A portion of belt410 passes through charging station A where a corona generating device,indicated generally by the reference numeral 422, charges thephotoconductive surface of photoreceptor belt 410 to a relatively high,substantially uniform, preferably negative potential.

Next, the charged portion of photoconductive surface is advanced throughan imaging/exposure station B. At imaging/exposure station B, acontroller, indicated generally by reference numeral 490, receives theimage signals from raster input scanner 428 representing the desiredoutput image and processes these signals to convert them to the variouscolor separations of the image which is transmitted to a laser basedoutput scanning device, which causes the charge retentive surface to bedischarged in accordance with the output from the scanning device.Preferably the scanning device is a laser Raster Output Scanner (ROS)424. Alternatively, the ROS 424 could be replaced by other xerographicexposure devices such as LED arrays.

The photoreceptor belt 410, which is initially charged to a voltage V₀,undergoes dark decay to a level equal to about −500 volts. When exposedat the exposure station B, it is discharged to a level equal to about−50 volts. Thus after exposure, the photoreceptor belt 410 contains amonopolar voltage profile of high and low voltages, the formercorresponding to charged areas and the latter corresponding todischarged or background areas.

At a first development station C, developer structure, indicatedgenerally by the reference numeral 432 utilizing a hybrid developmentsystem, the development roll, better known as the donor roll, is poweredby two development fields (potentials across an air gap). One example ofa hybrid development system is a hybrid jumping development (HJD)system. In a hybrid development system, the first field is the ac fieldwhich is used for toner cloud generation. In the HJD example, the acfield is an ac jumping field. In a hybrid development system, the secondfield is the dc development field which is used to control the amount ofdeveloped toner mass on the photoreceptor belt 410. The toner cloudcauses charged toner particles 426 to be attracted to the electrostaticlatent image. Appropriate developer biasing is accomplished via a powersupply. This type of system is a noncontact type in which only tonerparticles (black, for example) are attracted to the latent image andthere is no mechanical contact between the photoreceptor belt 410 and atoner delivery device to disturb a previously developed, but unfixed,image.

The developed but unfixed image is then transported past a secondcharging device 436 where the photoreceptor belt and previouslydeveloped toner image areas are recharged to a predetermined level.

A second exposure/imaging is performed by device 438 which comprises alaser based output structure is utilized for selectively discharging thephotoreceptor belt 410 on toned areas and/or bare areas, pursuant to theimage to be developed with the second color toner. At this point, thephotoreceptor belt 410 contains toned and untoned areas at relativelyhigh voltage levels and toned and untoned areas at relatively lowvoltage levels. These low voltage areas represent image areas which aredeveloped using discharged area development (DAD). To this end, anegatively charged, developer material 440 comprising color toner isemployed. The toner, which by way of example may be yellow, is containedin a developer housing structure 442 disposed at a second developerstation D and is presented to the latent images on the photoreceptorbelt 410 by way of a second developer system. A power supply (not shown)serves to electrically bias the developer structure to a level effectiveto develop the discharged image areas with negatively charged yellowtoner particles 440.

The above procedure is repeated for a third image for a third suitablecolor toner such as magenta (station E) and for a fourth image andsuitable color toner such as cyan (station F). The exposure controlscheme described below may be utilized for these subsequent imagingsteps. In this manner a full color composite toner image is developed onthe photoreceptor belt 410.

To the extent to which some toner charge is totally neutralized, or thepolarity reversed, thereby causing the composite image developed on thephotoreceptor belt 410 to consist of both positive and negative toner, anegative pre-transfer dicorotron member 450 is provided to condition thetoner for effective transfer to a substrate using positive coronadischarge.

Subsequent to image development a sheet of support material 452 is movedinto contact with the toner images at transfer station G. The sheet ofsupport material 452 is advanced to transfer station G by a sheetfeeding apparatus 500. The sheet of support material 452 is then broughtinto contact with photoconductive surface of photoreceptor belt 410 in atimed sequence so that the toner powder image developed thereon contactsthe advancing sheet of support material 452 at transfer station G.

Transfer station G includes a transfer dicorotron 454 which sprayspositive ions onto the backside of sheet 452. This attracts thenegatively charged toner powder images from the photoreceptor belt 410to sheet 452. A detack dicorotron 456 is provided for facilitatingstripping of the sheets from the photoreceptor belt 410.

After transfer, the sheet of support material 452 continues to move, inthe direction of arrow 458, onto a conveyor (not shown) which advancesthe sheet to fusing station H. Fusing station H includes a fuserassembly, indicated generally by the reference numeral 460, whichpermanently affixes the transferred powder image to sheet 452.Preferably, fuser assembly 460 comprises a heated fuser roller 462 and abackup or pressure roller 464. Sheet 452 passes between fuser roller 462and backup roller 464 with the toner powder image contacting fuserroller 462. In this manner, the toner powder images are permanentlyaffixed to sheet 452. After fusing, a chute, not shown, guides theadvancing sheets 452 to a catch tray, stacker, finisher or other outputdevice (not shown), for subsequent removal from the printing machine bythe operator.

After the sheet of support material 452 is separated fromphotoconductive surface of photoreceptor belt 410, the residual tonerparticles carried by the non-image areas on the photoconductive surfaceare removed therefrom. These particles are removed at cleaning station Iusing a cleaning brush or plural brush structure contained in a housing466. The cleaning brush 468 or brushes 468 are engaged after thecomposite toner image is transferred to a sheet. Once the photoreceptorbelt 410 is cleaned the brushes 468 are retracted utilizing a deviceincorporating a clutch (not shown) so that the next imaging anddevelopment cycle can begin.

Controller 490 regulates the various printer functions. The controller490 is preferably a programmable controller, which controls printerfunctions hereinbefore described. The controller 490 may provide acomparison count of the copy sheets, the number of documents beingrecirculated, the number of copy sheets selected by the operator, timedelays, jam corrections, etc. The control of all of the exemplarysystems heretofore described may be accomplished by conventional controlswitch inputs from the printing machine consoles selected by anoperator. Conventional sheet path sensors or switches may be utilized tokeep track of the position of the document and the copy sheets.

While FIGS. 6 and 7 shows one example of a digital document generatingdevice incorporating an assembly of photosensitive chips 10 andsupplemental photosensitive chips 11 it is understood that an assemblyof photosensitive chips 10 and supplemental photosensitive chips 11 maybe used in any digital scanning application of any digital documentreading, generating or reproducing device.

While the invention has been described in detail with reference tospecific and preferred embodiments, it will be appreciated that variousmodifications and variations will be apparent to the artisan. All suchmodifications and embodiments as may occur to one skilled in the art areintended to be within the scope of the appended claims.

What is claimed is:
 1. An assembly comprising: a substrate; a plurality of butted photosensitive chips mounted to the substrate along an array direction, wherein each photosensitive chip has an array of photosites including an edge photosite and wherein an abutment region is formed between the edge photosites of butted photosensitive chips and the butted photosensitive chips are not attached to each other; and at least one supplemental photosensitive chip mounted to the substrate and including a photosite located to receive light directed generally at the abutment region along a process direction perpendicular to the array direction.
 2. The assembly as in claim 1, wherein each photosensitive chip has a plurality of edge photosites.
 3. The assembly as in claim 1, wherein each of the photosensitive chips defines a plurality of photosites evenly spaced thereon, the photosites being positioned to form a linear array on the substrate.
 4. The assembly as in claim 3, wherein each of the supplemental photosensitive chips defines a plurality of photosites evenly spaced thereon.
 5. The assembly as in claim 1, wherein each of the photosensitive chips defines a plurality of photosites evenly spaced thereon, the photosites being positioned to form multiple parallel linear arrays on the substrate.
 6. The assembly as in claim 5, wherein each linear array on each of the photosensitive chips is covered by a translucent filter.
 7. The assembly as in claim 5, wherein each of the supplemental photosensitive chips defines a plurality of photosites evenly spaced thereon, the photosites being positioned and covered with translucent filter materials to correspond with multiple parallel linear arrays formed by the photosensitive chips.
 8. The assembly as in claim 1, wherein the supplemental chips are shorter than the photosensitive chips along the array direction.
 9. The assembly as in claim 1, wherein the supplemental chip includes a first set of photosites and a second set of photosites, the first set of photosites being filtered to receive light of a first predetermined color.
 10. The assembly as in claim 9, the second set of photosites being filtered to receive light of a second predetermined color. 